Metal resistivity has been known to increase in narrow trenches due to electron scattering from the surfaces in the trenches (also referred to as “surface scattering). As lines continue to narrow, the effects of electron scattering from surfaces significantly increase.
Beyond the 7 nm node, resistivity will be dominated by surface scattering over grain boundary and phonon scattering. For example, it is known that surface scattering can account for about 66% of the resistivity for 10 nm wide lines. As dimensions shrink, surface scattering will compose the majority of the wire resistivity. In other words, smaller dimensions will lead to increased surface scattering, which in turn will lead to increased resistance.
Accordingly, there is a need for viable methods to reduce surface scattering.